Both therapists I have worked with in the recent past have offered for me to throw things in their room, push against them, scream, spit (this was outdoors), physical stuff like that. I didn't necessarily do all of these things (with hindsight, I should have strangled one of them), but the suggestions were useful in themselves because they led to other pieces of work. It is often discussed that anger is a secondary emotion which acts as a protective response. It might be worth thinking about your primary emotion (even what fundamental emotion is contained/hidden in your complicated grief) and putting some physical action to that primary emotion which you could act out as part of the anger expression. For example, if shame if your primary emotion (it is often mine), you could assign the colour red to shame (red faced and embarrassed) and throw red paint around whilst screaming. I would like that for myself actually. Anyway, that's just an example, but you see what I mean.